1. Field of the Invention
The present invention relates to an actuator for converting the fluid pressure to the mechanical power of action, and more particularly it relates to a novel actuator which can be operated to serve concurrently or selectively as a rotary actuator and/or as a linear motion actuator.
2. Prior Art
Recently, actuators driven by pressurized fluids have been widely used as important mechanisms in automation systems, semi-automatic machines and various lavour-saving systems. Such actuators conventionally produced and commercially supplied for use may be classified into rotary actuators and linear motion actuators. However, an actuator which can be operated to serve concurrently or selectively as a rotary actuator and/or as a linear motion actuator has not yet been practically available by the prior art technique.
In the prior art, difficulty in fluid-tightly sealing the portion at which the rotational or rocking motion is picked out of the hydraulic or pneumatic cylinder, hinders the realization or a rotary actuator which may be highly efficiently and reliably operated. None of the conventionally available rotary actuators could avoid the disadvantageous leakage of the high pressure fluid without causing pressure loss due to friction at the sealing portion.
On the other hand, the prior art linear motion actuator exerting high power output is essentially composed of a piston and a piston rod integrally secured to said piston, so that, in installation of such actuator, a considerably large space area which is normally vacant when the actuator is not operated is necessitated in the longitudinal direction thereof for accommodating the stroke length of the outwardly projecting piston rod in addition to the length of the long cylinder to result in redundant increase of the space area necessary for accommodating the entire actuator mechanism. A further disadvantage of the prior art linear motion actuator is that a cooperative actuator system including a plurality of actuators cannot be assembled without using a balancing device for registering or adjusting the timing or operational positions of the plurality of actuators precisely. Without such delicate and expensive balancer, the prior art linear motion actuators cannot be combined in a multiple function actuator system. The final and most inconvenient disadvantage of the prior art linear motion actuator is that it is merely operated in a single mode function.
Under these circumstances, there is an increasing demand for an actuator which may be operated reliably at high efficiency with minimal pressure loss due to friction while being caused by no appreciable leakage of the high pressure fluid.